Reference is made to copending applications Ser. No. 511,704 U.S. Pat. No. 4,500,584 and Ser. No. 511,705 U.S. Pat. No. 4,472,470 of Frank J. Modic, both of which were filed July 7, 1983, and are assigned to the same assignee as the present invention.
The present invention relates to coated fabrics having improved strength and improved flame retardance. More particularly, the present invention relates to a method for improving the strength and flame retardance of silicone coated glass cloth by incorporating non-abrasive fillers such as calcium carbonate, hydrated alumina and the like into the elastomeric silicone coating.
The discovery that Teflon.RTM. coated fiberglass could be utilized as a noncombustible, durable roof structure has initiated a transformation from simplistic, temporary air-supported structures to one with evergrowing potential. The impetus for the development of such fabric membrane structures was to provide roofing for large sports facilities. This led to other roofing uses such as for department stores, shopping malls, schools, exhibition buildings, industrial structures and the like. While the Teflon-coated fiberglass system has many desirable features such as durability and dirt resistance, it suffers from the major deficiency that light (solar) transmission is limited to approximately 10 to 15% due to the opaqueness of Teflon.
Modic, in copending patent application, Ser. Nos. 511,704 and 511,705 filed July 7, 1983, provided roofing fabric membrane structures which overcome the light transmission problem of the Teflon-coated fiberglass system by utilizing a transparent or translucent base coating and a transparent or translucent dirt resistant coating. Modic further taught that a finely divided inorganic filler could optionally be included in the silicone coatings in order to adjust the translucency of the coated fiberglass fabric. The extent to which light transmission is reduced is determined by the quantity of filler utilized, i.e. more filler reduces the amount of light which passes through to the interior of the building or structure. Modic also taught that since the function of the finely divided filler is not to reinforce the composition, reinforcing fillers are generally not employed.
It has recently been found that the tear strength of the coated fabric was about the same or less than that of the original uncoated fabric when ground quartz such as Minusil.RTM. was employed as a filler on a fiberglass cloth. Quite unexpectedly, the present applicant has discovered that when certain non-abrasive fillers such as calcium carbonate and hydrated alumina are added to the base silicone coating composition, the tear strength of the coated fabric significantly increases. Moreover, the inclusion of such non-abrasive fillers in the silicone coatings surprisingly improves the flame retardance or flame resistance of the coated fabric.